PHILADELPHIA, Pennsylvania (CNN) -- The future of troops in Iraq and the potential of a U.S. showdown with Iran dominated much of Tuesday's Democratic presidential debate -- with front-runner Hillary Clinton's votes on the two issues at the center.

The New York senator and former North Carolina Sen. John Edwards had sharp exchanges on how to proceed in Iraq.

"If you believe that combat missions should be continued in Iraq over the long term, if you believe that combat troops should remain stationed in Iraq, and if you believe there should be no actual timetable for withdrawal, then Sen. Clinton is your candidate," Edwards said. "I don't. I think that we need to end combat missions; we need to get combat troops out of Iraq."

Clinton claimed that Edwards misstated her position, saying any further combat role would only be in pursuit of terrorists.

"My understanding is that we had the same agreement -- most of us on this stage -- that we would bring out combat troops, but we would pursue a mission against al Qaeda in Iraq, if they remained a threat.

"Now, I don't know how you pursue al Qaeda without engaging them in combat," Clinton said. "So I think we're having a semantic difference here. I think we should get as many of the combat troops out as quickly as possible." Watch the presidential hopefuls exchange jabs »

While Edwards and Illinois Sen. Barack Obama criticized Clinton's vote authorizing the war in Iraq, the debate Tuesday dealt heavily with a new vote -- her support of a resolution declaring the Iranian Revolutionary Council a terrorist organization.

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"I am not in favor of this rush for war, but I'm also not in favor of doing nothing. Iran is seeking nuclear weapons," Clinton said in defending her stance. "And the Iranian Revolutionary Guard is in the forefront of that, as they are in the sponsorship of terrorism."

Directly confronting her critics, the senator said, "So some may want a false choice between rushing to war, which is the way the Republicans sound -- it's not even a question of whether, it's a question of when and what weapons to use -- and doing nothing.

"I prefer vigorous diplomacy. And I happen to think economic sanctions are part of vigorous diplomacy."

Obama, who did not vote on the resolution, criticized it as premature.

"This kind of resolution does not send the right signal to the region," he said. "It doesn't send the right signal to our allies or our enemies. And, as a consequence, I think over the long term, it weakens our capacity to influence Iran.

"Now, there may come a point where those measures have been exhausted and Iran is on the verge of obtaining a nuclear weapon, where we have to consider other options. But we shouldn't talk about those options now, when we haven't even tried what would be a much more effective approach."

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Ohio Rep. Dennis Kucinich said supporters of the resolution are opening the door for war with Iran.

"There's no basis for it whatsoever," he said. "But we have to realize ... that we have a number of enablers who happen to be Democrats who have said over the last year, with respect to Iran, all options are on the table. And when you say all options are on the table, you are licensing President Bush."

New Mexico Gov. Bill Richardson advocated negotiations with Tehran without conditions, saying the world "cannot permit Iran to use nuclear weapons."

"[Iranian President Mahmoud Ahmadinejad] -- it's very difficult to deal with him -- but there are moderate elements in Iraq. There are moderate clerics. There's students. There's a business community," Richardson said. "And I believe that we can achieve a compromise on the nuclear issue.

Sen. Joe Biden of Delaware said it is important not to let Iran distract from other pressing issues.

"I will do all in my power to stop Iran from getting a nuclear weapon, but I will never take my eye off the ball," he said.

"What is the greatest threat to the United States of America: 2.6 kilograms of highly enriched uranium in Tehran or an out-of-control Pakistan? It's not close."

Sen. Chris Dodd of Connecticut said the situations amplify the need for foreign policy experience.

"Which of us here brings the background, the experience, the ability to make a difference on these issues, including the question of Iran," suggesting he was the candidate who could deliver that experience.E-mail to a friend